Final answer:
Upon touching, two charged conducting spheres equally redistribute the combined charge of -8 nC, resulting in each sphere carrying -4 nC. The electric force each exerts on the other is calculated using Coulomb's law, considering the new equilibrium charges and the distance between them.
Step-by-step explanation:
Charge Distribution and Electric Force between Conducting Spheres
When two conducting spheres are brought into contact and then separated, the charge redistributes equally between them. Sphere A has an initial charge of -5 nC and Sphere B has -3 nC. When they touch, the combined charge of -8 nC is shared evenly. After separation, each sphere will have half of the total charge, resulting in each sphere having a charge of -4 nC.
Calculating Electric Force: After reaching equilibrium and separation, each of the spheres exerts an electric force on the other based on Coulomb's law, which is inversely proportional to the square of the distance between them.
To find the electric force one sphere exerts on the other, we would use the formula for Coulomb's law, where the force is proportional to the product of the charges divided by the square of the distance between their centers.
Number of Electrons: Since the charge on each sphere is -4 nC, we can calculate the number of electrons by dividing the charge on one sphere by the elementary charge (approximately 1.6 x 10-19 coulombs per electron).